In gearing, the pitch curve of each solid is a circle (as in cylindrical or conical gearing); in rack and pinion systems, the pitch curve of the rack is a circle of infinite radius. In most cases, the profiles of the teeth with which said solids are equipped are involutes to circles of constant diameter (or a straight line in the limiting case of a rack).
With such an arrangement, when one of the solids is subjected to uniform rotation, the other solid is driven with uniform rotation under good conditions concerning the arc of contact of the gearing, and the angle at which the teeth cooperate (optimum strength relative to transmission forces), and, in addition, is easy to make. The arrangement of the toothing thus corresponds to requirements for so-called standard toothing.
There are other types of toothing which are applied to non-circular pitch curves (in particular elliptical curves) in which uniform rotation of one of the solids gives rise to non-uniform rotation of the driven solid. However, the forms of toothing implemented do not satisfy standard criteria and as a result have not been applied in industry.
The present invention seeks to provide standard toothing in which each tooth is defined by a profile satisfying the conditions mentioned above, concerning arc of contact, ability to withstand the forces to be transmitted, and ease of cutting, even through the pitch curves thereof (which may be open or closed) are neither circles or nor straight lines, thereby providing non-uniform motion of the driven solid about its axis of rotation, said motion thus including stages of angular acceleration or deceleration for uniform motion of the driving solid.